Maybe you can help - home remodeling question...

[Firethorn]

It's getting hot around here, at least for my northern sensabilities.  I'm considering installing an AC unit in my bedroom to cool and dehumidify.  One issue - slider windows, but I can get a unit for them online.  The room's small, just over 100 sq feet.  Call it 120 with the closet(and this is the master bedroom ).

So, checking units out, 5k BTU slider AC unit, ~$250.  More expensive than a regular window, but it's not like I have that much choice.

Here's the issue:  I have two outlets in the room, neither particularly close to the window.  One's next to the bed, has the light and alarm in it.  On the opposite wall(by the foot of the bed), is an outlet I installed myself.  Wasn't too bad - interior wall.

Of course, the window, being a window, is on an exterior wall - the wall with the blown in granular insulation.

Any advice for installing an outlet in a wall with granular insulation without letting all of it out?  Or would I be better off installing an odd looking outlet in the ceiling?  I'm picturing running wire from the outlet I installed earlier into the attic, over to ceiling close to window, install box.

By preference, I'd prefer to have it next to the window, of course.  Worst case, I temporarily install it using a heavy gauge extension cable for the one month a year I want it.

[cassandra and sara's daddy]

i've cheated in some older houses by dropping a line  from an existing outlet and hiding it behind the base board as i bring it around the room and back up in a new lo cation. i glue/caulk base to the wall since i believe i have a near 100% chance of hitting the wire if i nail base

[K Frame]

Investigate something called Wiremold.

Mom's house is loaded with the stuff because it's a 1903 brick Victorian.

I just did a new line into Mom's office on an exterior wall for an AC. The wiring in the room wasn't capable of handling the load of an AC and her computer.

I mounted a surface box to the exterior wall, went through the floor and into the ceiling in the kitchen, went between the old plaster and lath ceiling and the new drop ceiling to an interior wall that took me to the basement.

I was able to get a new 12/2 20-amp dedicated circuit in without too much trouble. Took me quite awhile, but I got it done.

[Grandpa Shooter]

You need to know the draw of the AC unit before you decide to plug it into a standard circuit.  Many houses were wired with either 14 gauge wire which is rated for only 15 amps, or the aluminum wiring which was never designed to carry much of a load.  A 20 amp circuit should have 12 gauge wire.  10 gauge wire will handle a 30 amp circuit.  If you have other things already pulling power on the circuit you tap into, you could easily overload the breaker.  If there is room on the main service you would be better off running a dedicated outlet for that AC unit.  The way to tell if there is room is to look and see if there are any knockouts still in the box.  That will not tell you how much draw you already have on the service, but will tell you if there are any places left to install another breaker.

You might be better off checking with a qualified electrician before risking overloading a circuit or your main service.

[Firethorn]

Grandpa - I'm looking at a 5k BTU unit, they're rated around 5 amps@115V.  Overloading the circuit is not a problem, expecially since whoever wired the place used 12 gauge copper.  The outlet I was thinking about stringing it off of is currently used for a CFL light and the vacuum.  And that's the entire circuit, run with 12 gauge, so it's rated at 20 amps.  As for the main service, I have plenty of room - I should know, I installed the thing myself after I caught the fuse box previously in the house sparking.

I'm utterly unconcerned about the electrical portion of it.

What I was looking for was some advice on how to get an outlet in next to the window, as I prefer not to use extension cords for that sort of stuff.  The wall's got granular insulation in it, so I can't just do the standard 'cut a hole in, drill a hole into the basement using my 6' .5 inch flexible drill bit, and pull the wire back through'.

But then, if I DO end up using a cord, it'll probably be one of the outdoor rated 12 or 14 gauge ones out in the garage.

It's sounding like surface mount on the wall, running to the ceiling might be my best option?

[K Frame]

Technically you do not need a 20 amp circuit until you get up to around 12,000 BTU, IIRC.

Once you get above... 20,000 (?) BTU you need to go 240.

That said, I agree with Leatherneck's assessment in a message to me a couple of weeks ago when he says that he believes that anything with a "start-up" electric motor on it (fridge, freezer, AC), should go on a 20 amp circuit even if 15 amp is indicated as being fine.

It gives you a lot of excess capacity on the circuit and adds virtually no cost at all. The biggest problem with the 12 gauge wire required by a 20 amp circuit is that it's a lot stiffer than 14 gauge, and thus is more difficult to pull through wall cavities.

[K Frame]

"expecially since whoever wired the place used 12 gauge copper."

OK, they used 12 gauge copper...

Did they use the proper 20 amp receptacles, and is it connected to a 20 amp breaker? 


"But then, if I DO end up using a cord, it'll probably be one of the outdoor rated 12 or 14 gauge ones out in the garage."

No.

Buy a cord SPECIFICALLY rated for an air conditioner in only the length you need.

[Firethorn]

Did they use the proper 20 amp receptacles, and is it connected to a 20 amp breaker? 

If they weren't before, they are now.  I've replaced many of the outlets.  The specific circuit I'd be putting it on is 100% installed by me, is 12 gauge copper, and on a 20 amp breaker.

Buy a cord SPECIFICALLY rated for an air conditioner in only the length you need.

What's the difference?  Honest question.  I've never seen a cord rated for air conditioner use.  I've seen them rated by amps/wattage, but not for any specific duty.

[K Frame]

"What's the difference"

The startup surge draw capacity.

When the compressor kick in, it can draw significantly more than the rated amperage for upwards a second.

General use power cords generally don't have the capacity to deal with the power draw when the compressor starts. They're great for running weed whackers and other such items.

In severe cases, you can actuall damage the compressor. That's not nearly the factor today with the new breakered plugs that they're putting on ACs, but you could end up repeatedly tripping the cord breaker.

Outdoor use extension cords also tend to be overly long, which can only make the problem worse.

[Firethorn]

The startup surge draw capacity.

I understand about not using a zip cord extension cord.  I have a tendency to buy good extension cables when they come on sale - I don't OWN any zip cord extension cables.  I'm just curious, can you point out a specific difference in construction that would render my heavy duty extension cord unsuitable?  I mean, 12 gauge copper is 12 gauge copper, right?  After that you have things like sheath construction for various levels of heat and wear resistance, and outdoor cables tend to win both matchups.

General use power cords generally don't have the capacity to deal with the power draw when the compressor starts. They're great for running weed whackers and other such items.

I wasn't talking about using a 'general use' one, I was talking about a heavy duty outdoor rated 15 amp, and I'm not about to try using a 50 footer - the one I'm thinking of is 12-15'(can't remember exactly).

Do I really have to worr about requiring a special power cord for an AC unit, but I don't when powering This 15amp chop saw?

[K Frame]

Were I talking about zip cord type extension cords, I would have said light duty or zip cord extension cord. But I don't recall using either of those terms.

Ask the manufacturer of either the cord or the appliance for specifics on construction or ratings.


As for extension cords, a cord designated as an "outdoor" extension cord is, by definition, a general use extension cord.

Here's something from the CPSC that may answer some of your questions.

http://www.cpsc.gov/cpscpub/pubs/16.html



As for the chop saw...

I sincerely doubt that that saw comes even remotely close to drawing the momentary surge amperage that even a small air conditioner compressor draws.

[Firethorn]

Here's something from the CPSC that may answer some of your questions.

http://www.cpsc.gov/cpscpub/pubs/16.html

According to that site, my cord would be just fine - not getting pressed up against, not buried in stuff, not being stepped on, wattage/amperage rating well in excess of the stated capacity stated on the AC unit.

As for my chop saw - it says 15 Amps, vs the AC unit, which says 5.  Why would the compressor, which is essentially an electric motor, draw more juice than the chop saw rated at three times the amperage?  Isn't the draw rating on the panel supposed to be the max draw?

[cassandra and sara's daddy]

what kinda siding on outside of house?i've run circuits with uf wire under vinyl be scared to do it with aluminum. i also makemy own cords sometimes  can get the length just right for a longterm application. the only fly in the ointment as far as the cords i can see is the saw draws a short time the compressor for long periods. the worry i have is temperture related. if the cord heats up the insulation breaks down and the conductive properties change as well . i can't tell you how many warm cords i've seen as well as a few that were hot enough to soften casing

[K Frame]

"Isn't the draw rating on the panel supposed to be the max draw?"

No.

Start up surge amperage can be quite a few times higher than the operational amperage. The important factor is how many amps the motor draws during continuous operation.

And your chopsaw motor is RATED at 15 amps draw at full load capacity.

In other words, it's a 1.5 horse power motor.

It doesn't draw 15 amps during operation. Nothing even close to it.

If you were to crack the casing on your air conditioner, you'd find a rating tag on the motor, similar to the one on your chop saw, that would give the full-load amperage, which can be translated into the horse power. Or, it might give a horsepower rating, which can be translated back to full-load amperage.

[Firethorn]

what kinda siding on outside of house?

Old wood siding.  I'd be afraid to take it off because of the granular insulation issue - they drilled holes in it and blew it in or something.  I can see the caps.

Start up surge amperage can be quite a few times higher than the operational amperage. The important factor is how many amps the motor draws during continuous operation.

And your chopsaw motor is RATED at 15 amps draw at full load capacity.

I still believe that the voltage/amp label mounted on the unit is for MAX draw - why would the AC label have the continous draw amperage and the chop saw the Max?  Heck, I'm looking at a computer that's rated at 5 amps@120V, but draws about .5 in operation.

The biggest risk to extension cords is heat - I'm not about to keep using an extension cord that gets hot.  The momentary draw isn't going to be a big deal unless it's enough to heath things up enough to damage the insulation in the brief period of it starting up.

[Leatherneck]

I'd be inclined to avoid the extension cord because they tend to get (inadvertently) abused by shoes, pets, vacuum cleaners, furniture, etc, and they are vulnerable to plug loosening and movement which can cause arcing at the prongs. I'd be much more comfortable with 12 GA NMC, either in the wall or in a wiremold run.

TC

[K Frame]

" still believe that the voltage/amp label mounted on the unit is for MAX draw - why would the AC label have the continous draw amperage and the chop saw the Max?"

Because the two motors are not used in the same way, and the rating tags are telling you two completely different sets of information.


The rating on your saw motor is just that, the rating on the saw motor, which is being used in a completely different manner.  

On the air conditioner there are normally other electrical draw issues involved in the operation of the unit, so the rating is for the entire unit as a whole, not just the motor.

At least that is my understanding.



"The biggest risk to extension cords is heat."

And the biggest risk to your AC compressor is the inability of the cord that you choose to supply the current it needs to get through the start up surge.

[Firethorn]

I'd be inclined to avoid the extension cord because they tend to get (inadvertently) abused by shoes, pets, vacuum cleaners, furniture, etc, and they are vulnerable to plug loosening and movement which can cause arcing at the prongs. I'd be much more comfortable with 12 GA NMC, either in the wall or in a wiremold run.

It's just me, I don't walk there, no pets, I'm not moving the furniture, and tend to use good quality sockets for a good grip fit.  It looks like the wiremold run is my best option, though.

Mike,

I still believe that the requirement for the label is that it has to show max draw of the unit - not the average one.  The fact that it's for the entire unit as a whole just means that it has to include the control panel, the fan motors, etc in the amperage figure, not just the compresser.  If anything that makes it easier - less likely to actually draw the max.

And the biggest risk to your AC compressor is the inability of the cord that you choose to supply the current it needs to get through the start up surge.

And how is a 12 gauge extension cable going to have less current capacity than the 14 gauge NMC going from the outlets some people will be plugging the 5 amp AC into?  Than the likely 14 gauge power cord that comes with it?

[K Frame]

Important information, from this site, and a concept that I've been trying to get across:

http://sawdustmaking.com/ELECTRIC%20MOTORS/electricmotors.html


"Not all motors are rated the same, some are rated under load, others as peak horsepower, hence we have 5 HP compressors with huge motors and 5 Hp shopvacs with tiny little motors."

The important information there is motors are NOT rated the same for every application.

That's why you're seeing differences between your chop saw and your air conditioner.

[K Frame]

"I still believe that the requirement for the label is that it has to show max draw of the unit"

And, again, that is incorrect.

http://www.rcgroups.com/forums/showthread.php?t=575829


I believe there's a rather complex formula that can be applied to figure out just how much start up draw there will be when a motor kicks in.

[Nick1911]

On a somewhat related note, isn't it wild how distorted motor ratings are?

In magical perfect physics world,  a 5 hp would require 3728.5 watts.  Which is 31 amps on a standard 120V household system.  So, if you're shop vac has a 5hp motor, and runs off a 20 amp circuit, either the rating is the max-right-before-it-melts power, or it's lying.

Probably a little of both, actually.

[ilbob]

"expecially since whoever wired the place used 12 gauge copper."

OK, they used 12 gauge copper...

Did they use the proper 20 amp receptacles, and is it connected to a 20 amp breaker? 

There is no reason why you have to use 20A receptacles just becasue you pulled #12 cu.

The code allows you to put 15A outlets on 20A circuits as long as there are at least two of them, even if both of them are on the same yoke (i.e.-a duplex outlet counts).

[Leatherneck]

Hey Bob, I'm glad to learn that. But I have a question: If I saw that the circuit was rated for 20A, but didn't notice the outlets were 15A, and I plugged in a 20A load, what would the outlet do? Hazard?

TC

[280plus]

Hey Bob, I'm glad to learn that. But I have a question: If I saw that the circuit was rated for 20A, but didn't notice the outlets were 15A, and I plugged in a 20A load, what would the outlet do? Hazard?

TC

If you draw more than 15A through it it'll overheat and will eventually burn out. I've seen plenty of "roasted" looking 15A outlets that had heavy motors drawing too much on them. So while the rest of the circuit may be able to handle 20 amps the 15A outlet will fry if you put more than 15A through it for any length of time.

As far as motor starting amps. I'm not real sure on the chop saw motor but I can tell you rule of thumb is it takes 6 times the run amps (RLA or FLA on the tag) to start an A/C compressor, this equals "LRA" or "Locked Rotor Amps" which is the amperage it will draw if it is powered and the rotor is stationary. I BELIEVE all motors will momentarily draw locked rotor amps upon start up because at the moment of start up the rotor is stationary. Once it begins to move amps drop off at a rate determined by how long it takes the rotor to come up to full speed, usually quite rapidly.

Yes, all appliances that draw large amperage on startup should each be on their own properly rated circuit because you don't want the circuit to ever have to try and start, for example, your fridge and your A/C simultaneously, this would WAY overload the circuit. Generally, if I see a tag that only gives me FLA or RLA I would multiply that number by 6 to get a rough idea of the start amps needed.

I think the vacuum motor / 31Amp question has to do with the difference in math when you figure resistive load vs inductive load. You may be doing the math for resistive load to come up with the 31 amps. Just a wild ass guess though.

Hope this helps. 

[Firethorn]

Hey Bob, I'm glad to learn that. But I have a question: If I saw that the circuit was rated for 20A, but didn't notice the outlets were 15A, and I plugged in a 20A load, what would the outlet do? Hazard?

The '15A' premium outlets I got are actually rated for 20A, they just don't have the keyed slot for a 20A plug.  I personally got them because they're easier to hook up than the cheap ones, not to mention plugging stuff into them is more pleasant.  Both easier to insert and better holding.

That's the other thing - it'd be difficult to load one with 20A on one plug, as plugs over 15 are to be keyed - one of the teeth is turned sideways.

280plus,

If they take that much more power, shouldn't they be capacitor start?  Thus lowering the starting load by a huge amount?

And what does FLA or RLA stand for?